In previously issued U.S. Pat. Nos. 4,865,817, 4,963,329, 5,023,064 and 5,192,517 as well as concurrently pending U.S. patent applications Ser. Nos. 672,021 now U.S. Pat. No. 5,362,464 and 754,643, all assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is disclosed a gas reacting apparatus and method for the wet mass transfer of solute gases from a gas stream to a liquid reacting medium capable of chemisorption of the solute gases from or contained in the gas stream.
The basis of the above patents and applications and also why the unique approach to gas absorption described therein works so effectively relates to the exceptionally large surface area of liquid absorption medium in the form of very small droplets of the liquid absorption medium generated in-duct with two-phase atomizing nozzles or certain hydraulic nozzles or any other device which will create a spray of fine droplets. Accordingly, there have been developed commercial applications of such technology for the removal of acidic gases, such as SO.sub.2, H.sub.2 S, Cl.sub.2, ClO.sub.2, NO.sub.x, HCl, HF, SO.sub.3, etc. using a variety of absorption media. In most of these applications, the absorption media chemically react with the acidic gas, sometimes to oxidize it or reduce it or otherwise to form a stable reaction product, that may be disposed of or otherwise treated for disposal. Apparatus embodying such techniques is known by our assignee as the "Waterloo Scrubber".
In some cases of such solute gas absorption process, the absorption media can be regenerated. Often, the regeneration step is accomplished by steam stripping in more or less conventional tray or packed columns. This steam stripping regeneration procedure is an industrial process step that is widely used throughout the chemical industry for many differing desorbing or separating requirements, and not simply for the regeneration of absorption media used to remove solute gases by the procedures described in the above patents and applications.
The steam which is used in such stripping operations usually is generated in a reboiler located at the base of the conventional tray or packed column and rises in counter-current flow to the loaded liquid absorption medium, which normally is fed to the middle of the column and passes tray-to-tray or over the packing down the column. Overhead product reflux generally is employed to further purify the overhead product. The steam (gas)liquid contact in such operations where a tray column is employed is confined to the interfacial area generated as the bubbles of steam pass through the shallow layer of liquid absorption medium covering each tray in the column. In normal practice, each equilibrium stage represents a number of trays. The number of equilibrium stages required to effect separation of the absorbed component varies and is dependent on the particular system under consideration, i.e. vapor-liquid equilibrium data and specific operating conditions.